1. Field of the Invention
The present invention relates to video display devices, and more particularly, to circuit and method for compensating a display defect in a video display device which can reduce a size of a memory which stores a compensation data on a plurality of regular patterned defective regions.
2. Discussion of the Related Art
Currently, as the video display devices, flat display devices, such as liquid crystal display device LCD, plasma display panel PDP, organic light emitting diode OLED, are used, mostly.
The video display device passes through an inspection process for detecting a display defect after finishing fabrication of a display panel which displays a video. Though the display panel having the display defect passes through a repair process for the defective portion, there can be display defect that can not be repaired even in the repair process.
The display defect is caused mostly by variation of exposure quantity come from superimposition of the exposures and aberration of multi-lens at the time of multi-exposure by an exposing apparatus used in a thin film pattern forming process. The variation of exposure quantity causes variation a width of the thin film pattern, to vary parasitic capacitance of the thin film transistor, a height of a column spacer which maintains a cell gap, and parasitic capacitance between signal lines. The variation causes brightness variation on a displayed video, resulting in the display defect. The display defect caused by the variation of exposure quantity is displayed on the display panel in transverse lines or longitudinal lines depending on a direction of the scan of the exposing apparatus. The display defect in a form of the transverse lines or longitudinal lines can not be solved even with modification of a process technology.
Moreover, the display defect can be displayed as a point defect from a defective pixel having foreign matters infiltrated therein. Though the defective pixel is repaired in the repair process, the point defect takes place even from the repaired pixel. For an example, if the defective pixel is turned into a dark point in the repair process, the pixel turned into a dark point can be displayed as a black point defect in a white mode video. If the repair process is performed, in which the pixel turned into a dark point is linked to an adjacent regular pixel, requiring that a data supplied to the regular pixel is spread and charged even to the repaired pixel linked thus to each other, it is liable that the linked pixels can be displayed as a point defect due to shortage of a data charge quantity.
A method is taken into consideration, in which the defect is compensated by a compensation data by means of a circuit. For an example, the Korean patent application No. 10-2006-0059285 filed by the applicant discloses a method for compensating a data to be displayed at a display defective region by a method in which the data to be displayed at the display defective region is converted by using the compensation data.
In order to make a large sized liquid crystal display device slimmer, which requires a direct lighting type back light unit, a gap between the liquid crystal display panel and the back light unit is reduced. According to this, due to shortage of a diffusing path from the back light unit, the liquid crystal display device can display a display defect in a form of transverse lines along positions of a plurality of lamps. For an example, the liquid crystal display device having 26 lamps applied thereto may have 26 lines of the transverse line defect due to the lamps. In this case, in order to compensate the 26 transverse line defect regions caused by the lamps respectively, it is required that a compensation data on each of the 26 transverse line defect regions is in storage according to defect levels. That is, a related art memory has a plurality of defect level data and a plurality of compensation data sets on each of the defect level data stored in a storage space for each of a plurality of regular patterned defective regions. According to this, if a number of the defective regions increases, a size of the compensation data increases, to increase a size of the memory, the related art compensation circuit has a production cost increased.